Motor control circuit



Aug. 29, 1933. D R

MOTOR CONTROL CIRCUIT Filed Sept. 3, 1931 J 51V INVENTOR John D. BY

Ryder.

Fig. 5

ATTORNEY Patented Au 29, 1933 UNITED STATES PATENT OFFICE Bailey MeterCompany,

Delaware a corporation 01' Application September 3, 1931. Serial No.561,006

11 Claims.

My invention relates to motor control cir cuits and has specialreference to providing an improved system for the stopping, starting,re-

versing and speed control of a normally coni stant-speed motor, such forexample as a direct-current motor.

In the invention I utilize a standard shuntwound direct-current motor,reconnected so that the field is separately excited with directl currentand the armature of which is connected in an alternating-currentcircuit. I arrange the armature circuit so that normally the armature isenergized by alternating-current but the opposing and equal torques ofthe opposite polarity of each half cycle prevent rotation of thearmature. By the converter action inherentin certain thermionic valves Iarrange such 'valves to allow a pulsating direct-current to flow throughthe armature circuit in one direction or the other as desired, resultingin rotation of the motor in one direction or the other. Such rotation isinitiated by releasing one of the opposing torques from the armaturecircuit thereby allowing a pulsating direct-current comprising one-halfof the alternating-current wave of desired polarity to flow through thearmature. A reversal of rotation of the armature is accomplished throughsubstituting therefor the other half of the alternating-current wave.

A substantially instantaneous stoppage of the motor is accomplishedthrough plugging action by returning the circuit to full-wavealternating-current from pulsating direct-currents of either polarity,which application of alternating-. current directly across the armatureresults in a substantially instantaneous stoppage of rotation of thearmature.

The motor, having a separately excited directcurrent field, rotates indesired direction depending upon the polarity of the half-wave oi thealternating-current or pulsating direct-current applied to the armature,and at a speed dependent upon the preponderance of the rotating torqueover the motor load and friction, and where the rotating torque is thedifference between the line-E. M. F. and the counter-E. M. F. Whenalternating-current is applied to the armature, the pulsating current ofopposite polarity, comprising the opposite half-wave of thealternating-current, immediately subjects the armature to a stoppingtorque tending to cause rotation in the opposite direction, and of avalue equal to the summation of the line-E. M. F. and the counter-E. M.F. or substantially double the 55 value of the rotating torque. Thus therotating torque is substantially instantaneously opposed by a stoppingtorque of far greater magnitude and stoppage of rotation occurssubstantially instantaneously and without appreciable overtravel. 30

I provide in my arrangement in the armature circuit means knowngenerally to those familiar with the art as the phase-shifting method ofcurrent control, whereby I can obtain a rotation of the armature ineither direction at prac- 85 tic-ally any speed up to a maximum.

I further provide in my improved motor control circuit means preventinginjury to the direct-current motor when full-wave alternatingcurrent isapplied across the armature.

Further features of the invention will appear from the followingdescription in which certain preferred embodiments of the invention areexplained more fully with reference to the accompanying drawing.

In the drawing:

Fig. 1 represents somewhat diagrammatically one embodiment of theinvention.

Fig. 2 is a similar drawing embodying a slight modification of thearrangement of Fig. 1.

Fig. 3 represents somewhat diagrammatically a further embodiment of theinvention.

Fig. 4 represents diagrammatically a fragment of an embodiment.

Fig. 5 represents a somewhat different arrangement of the fragme t shownin Fig. 4.

Referring first to Fig. 1, illustrate as one embodiment of the inventionthe automatic op eration of a motor control circuit in accordance withthe momentary value of a variable to be regulated, such for example asthe pressure of a fluid flowing through a conduit 1,-which pressure at apoint 2 in the conduit is eflective for positioning a Bourdon tube 3,and to be maintained substantially uniform through the poas sitioning inthe conduit of a damper or valve means 4. For positioning the damper Iprovide a normally stationary motor having a field 5 and an armature 6,the latter being connected in an alternating-current circuit. I energize1% the field 5 from a direct-current source through a single poleswitchindicated at' 7.

The main features of the invention lie in the control and supply ofalternating-current to the armature, to. cause the armature to move 105from a position of rest in one direction or the other at a constantspeed or at a speed variable with some controlling function, and when itis desired to stop such rotation to accomplish the same with a minimumof overtravel on the part lid oi the armature through the use ofplugging or substantially instantaneous stopping. I provide a controlsystem wherein I cause a factor or relation of factors which are to becontrolled or maintained at a predetermined value to cause a deviationor departure of an element from a predetermined position when' thefactor or relation of factors departs from ,the predetermined value.Such movement of 'a member from a predetermined position to control thestarting of the motor and direction of its rotation, as

well as the speed with which the motor operates. For example, the speedof rotation may be directly proportional to the distance irom thepredetermined position in either direction, or bear any functional ordesirable relation thereto.

For the armature 6 I provide a source of alternating-current 8 availablethrough a hand operable two-pole switch 9 to the motor circuit proper.In the armature circuit I provide two oppositely connected three elementelectronic,

in the opposite direction. Thus with the two valves oppositelyconnected, in parallel with each other, and in turn in series with thearmature across the source 8 of alternating-current, the valves whenboth conducting will pass through the armature full-wavealternatingcurrent, thereby applying -to the armature equal torques inopposite directions, while with only one. valve conducting that valvepasses to the armature half-wave pulsating direct-current in a givendirection.

I indicate such thermionic valves at 10 and 11, having plate anodes 12and 13, control grids 14 and 15, and heated filament cathodes 16 and 17respectively. The cathode 16 of the one valve is connected to the anode13 of the other while the anode 12 of the one is connected to thecathode 17 of the other. These two interconnecting circuits are joinedbetween the thermionic valves by two resistances, 18 and 19, of equalvalve and connected in series; their purpose serving to equalize thepotential of the grids relative to their respective cathodes and thusinsure the motor running at the same speed ineither direction.

, Y'Ihe first-mentioned circuit joining the cathode 16 to the anode 13,further joins one pole of the armature 6, while the other pole of thearmature connects to the source of alterhating-current at the switch 9through a curused, the second named circuit between the thermionicvalves connecting the anode 12 with.

the cathode 17 is joined to the opposite pole of the alternating-currentsource switch 9.

For heating the filament cathodes 16 and 17 I. provide transformers 21and 22 respectively,

both being connected across the altematingcurrent supply.

The reactor 20 in the armature circuit serves to protect the armaturefrom excessive heating when alternating-current is impressed directlyacross the motor, as is the case when both thermionic valves 10 and 11are conducting. When direct-current flows through the motor armature thereactor saturates and practically all of the voltage exists across themotor for operation of same. 0n alternating-current, however, thereverse is true, and with practical- 1y all of the voltage across thereactor the motor heating'is very small.

I provide in connection with the Bourdon tube 3, and to be actuatedthereby, a contactor device 23 adapted to be positioned about a fulcrumintermediate its ends by the Bourdon tube, to the and that as shown inthe drawing, if pressure within the conduit 1 increases, then thecontactor bar 23 will tend to rotate in a counter-clockwise directionthrough actuation from the Bourdon tube, while if pressure within theconduit 1 decreases, rotation in a clockwise direction will result. Thecontactor normally is close-circuited at the contacts 24 and 25, joiningthe grid 14 and the grid 15 with the midpoint between the resistances 18and 19. In-

circuit between the grid 14 and the contact 24 being a resistance 26 andin circuit between the grid 15 and the contact 25 a resistance 27,namely grid current limiting resistances.

With the contacts 24 and 25 normally closecircuited the valves 10 and 11are normally conducting when the switch 9 is closed andalternating-current is available at 8. The cathodes 16 and 1'7 areheated and full-wave alternatingcurrent is impressed across the armature6 for the half-wave of one polarity through the valve 10 and thehalf-wave of opposite polarity through the valve 11 due to the oppositeconnecting oi the two valves relative to each other in the circuit. 1

The operation of such thermionic valves and their grid control is suchthat for a given plate voltage there is a particular grid voltage atwhich ionization will just occur, thus allowing the valve to passcurrent. It the grid potential iscurs and the valve passes current,providing the.

anode is positive with respect to the cathode. Thus the circuit isactive only when the respective anodes are positive and the resultantoutput of the valves and corresponding input to the armature is foreach'valve a half-wave pul-. sating direct current. For each valve oncethe.

anode current is started, the grid has no appreciable efiect on it. Thegrid cannot limit or stop the flow of current, but can regain control tokeep it from starting again if the flow ceases long enough for themercury vapor or gas to deionize. If an alternating-current voltage isapplied to the plate the grid has an opportunity of regaining controlonce each cycle and can delay the start of the are for as long a periodduring the cycle as the grid is sufliciently negative.

When the grid circuit of one of the valves is opened through the openingof the contact 24 or of the contact 25, the corresponding valve becomesinoperative, and its alternating-current half-wave is no longerimpressed across the armature 6 whereby the remaining valve supplies tothe armature the other half-wave or a pulsating direct-current of agiven polarity for rothrough the valve. .'avalve in only one direction,and inasmuch as the two valves 10 and 11 are oppositely connected tationoi the armature in a predetermined direction. Should the oppositecontact be opencircuited then the alternate valve is efiective andpulsating direct-current of opposite polarity is impressed across thearmature for rotation 01' the same in the opposite direction. Thus froma position of rest of the armature in which is impressed across italternating-current offullwave value I may cause a rotation of the motorin one direction or the other by positioning the contactor 23 aroundits-fulcrum and thereby cause an open-circuiting'oi the contact 24 or ofthe contact 25 in accordance with which direction of rotation I desirefor the armature.

Thus in operation, as the pressure oi the fluid in the conduit 1 at thepoint 2 deviates from that desired, the said deviation from the desiredvalue is felt upon the Bourdon tube 3 for positioning the contactor23froma predetermined position corresponding to the desired pressure.Such positioning will cause an open circuiting of either the contact 24or the contact 25 to result in a rotation of the armature in onedirection or the other for an opening or closing of the damper 4 torestore the pressure at the point 2.

Inasmuch as I supply both the grid and the plate of each valve with analternating-current, the phase 'relation between the grid and platevoltage determines the point in the wave at which current begins to passin each cycle, hence the average amount of current passing Current canpass through in parallel in the alternating-current circuit shown, eachvalve will pass one-half of the alternating current wave and I may varythe amount of current passing through each valve by causing a shiftingof the phase of the grid voltage relativ'eto the plate voltage and whichmay be accomplished by varying the inductance and/or the resistance inthe respective grid circuits.

In the arrangement illustrated in Fig. 1 I insert between the joiningpoint of the resistances 18, 19 and the contactorbar 23 an inductancecoil 28 in which is positioned a core 29 suspended from and positionedby the 'fulcrumed contactor beam 23. The arrangement is such that in theneutral position of the contactor bar 23, corresponding to apredetermined pressure of fluid in the conduit 1, and wherein thecontacts 24 and '25 are close-circuited the core 29 is in midposition ofthe coil 28 and a definite inductance is in the circuit.

Further in the circuit I show the resistances 30 and 31, the .former.joining the contact 24 with the cathode 16 and the latter joining thecontact 25 with the cathode 17. I accomplish a variation such as anincrease in speed of the motor by decreasing the inductance with theresistance 30 or 31 remaining constant (Fig. 1), while I accomplish anincrease in the speed 0! the motor in an alternate manner (Fig. 3), byholding the inductance constant and increasing the value of theresistance 30 or 31 of the corresponding circuit. The inductance isefiective between the plate and the grid, while the resistance becomeseffective between the grid and the cathode. In Fig. l I show the possibility oi varying the value of the inductance through the positioning ofthe core 29 from a mid-position within the inductance coil 28 and with aconstant value of resistance of 30 and 31.

In Fig. 3 I show a somewhat similar arrangement wherein the inductanceis maintained constant while I may vary the value of the resist- In Fig.2 I show an embodiment of my-invention wherein the circuit is identicalwith that of Fig. 1 except that I have provided the contactor 23.withnormally open-circuited contacts 24A and 25A rather than with theclose-circuited contacts 24 and25 of Fig. 1, which might be desirable incertain mechanical arrangements or for other reasons. The, arrangementprovides an open-circuited normally dead armature and normallynon-conducting or dead thermionic valves, varying from Fig. 1 whereinthe tubes are normally energized. and conducting and the armature isnormally alive with full-wave 9.1- ternating-current passingtherethrough. In Fig. 1 with full-wave alternating-current passingthrough the armature 6 I make inefiective one of the valves to cause arotation of the armature in a desired direction from pulsatingdirect-current of a given polarityimpressed across the armature andcause a substantially instantaneous stoppage of rotation of the armaturewhen the other valve is made to conduct through the application to thearmature of equal and opposite torques; In Fig. 2 with a normallydeenergized armature 6 I do not accomplish the plugging action ofthrowing across the armature the opposing equal torques, but thestopping of the motor is accomplished through the fact that as thecontactor bar approaches its neutral position the inductance core 29returns to its neutral position wherein the motor speed 1 is smoothlyreduced to zero. I

With the arrangement in Fig. 2 of the contacts 24A and 25A normallyopen-circuited, I permit one or the other of the valves to conductcurrent through the closing of either the contact 24A 1' or the contact25A to impress across the armature a pulsating direct-current of desiredpolarity and in amounts varying'substantially from zero to maximumthrough a shifting of the phase relation between the grid circuit andthe plate circuit as previously explained, by the positioning of thecore 29 in one direction or the other within the coil '28 from amidorneutral position.

In Fig. 4 I show a solenoidcore' 2 9A which has been coned down orshaped at the ends so that as the core is positioned from a midpointwithin the coil 28 the inductance of the circuit may vary in other thanlinear relation wherein I may accomplish a variation in speed throughoutsubstantially the rangeof zero to maximum in a variable or a functionalmanner as desired. In Fig. 3 is illustrated an embodiment of theinvention'wherein the circuit isidentical with that of Fig. 2 exceptthat I have provided the 1 inductance 28 with a fixed core 29B and havereplaced the fixed resistances 30 and 31 with variable resistances 30Aand 31A respectively. The contact beam 23 has an insulated extension ateach end adapted to cooperate with there- 1 sistances 30A and 31Awhereby as the contactor arm 23 is positioned around its fulcrum thecontacts 24A and 25A are not only closed butthe corresponding resistance30A or 31A is varied so that an increase in speed of the motor from a 1duit 1 at the point 2 should decrease below a predetermined value, thenthe Bourdon tube 3 will tend to move in a counter-clockwise direction atits free end, thus positioning. in a clockwise rotation the contactorarm 23 whereby the contact 24A will be close-circuited for a starting ofthe motor armature 6 in a given direction of rotation and at a speedcorresponding to the then position of the'left-hand end of the arm 23relative to the variable resistance 30A, such pobe other than a linearrelation to the pressure within the conduit 1;

' The invention may be employed with motors wherein the field isenergized my pulsating direct-current as well as continuousdirect-current. I preferably employ an alternating-current at 8 of avalue of twice the potential of the direct-current controlled by theswitch 7 which through the half-wave rectification results in a voltage,during rotation of the armature, across the armature of approximately45% of the value of the potential at the source 8 or substantially thesame'potential as is applied to the field 5. It is not necessary,however, that such voltage relationship obtain between the field and thearmature, for by varying such relationship as well as other adjustmentsof the circuit I may vary the basic speed of the motor.

In any of the embodiments described or others which may be employed tofunction with my invention, desirable values of resistances, reactance,etc. may be used and the invention is not limited to definite valuesthereof. I contemplate broadly a circuit of the nature disclosed Whereinnormally a motor has a direct-current energized field and normally hasalternating-current impressed across its armature wherein the armatureremains without rotation and without damage through excessive heating.However, when desired and through the functioning of the particularapparatus and arrangement of same, a pulsating direct-current of onepolarity or the other may be impressed across the armature of the motorto cause rotation thereof in a desired direction. Furthermore, when itis desired to stop the motor the motor may be plugged by the throwingacross the armature of alternatingcurrent of full-wave value rather thanhalfwave value of one polarity or the other, and thus through theapplication of opposing equal torques the motor is substantiallyinstantaneously plugged to a standstill without overtravel or creep.

I further contemplate a control of the speed of rotation of the motor ineither direction throughout substantially a complete range from zero tomaximum through the automatic variation of inductance and/or resistancein the thermionic valve circuit wherein a phase shift is accomplishedbetween the voltage of the plate circuit and the voltage of the gridcircuit, and that such speed variation may be other than linear inrelation to its control, I may attain a stoppage of the motor graduallythrough a speed control down to a minimum or zero condition of rotation.

Throughout the specification and claims where I speak of direct-currentor alternating-current, I use these terms in the commonly acceptedmanner and meaning. By direct-current I mean a unidirectional flow, beit continuous, intermittent or pulsating, and by alternatingcurrent Imean one wherein the flow periodically alternates as to. direction orpolarity.

Certain subject matter pertaining to the plugging of a direct-currentenergized motor armature with alternatingcurrent for accomplishing asubstantially instantaneous stoppage of rotation of the armature,disclosed but not claimed herein, forms the basis for my co-pendingapplication Serial No. 561,005 filed of even date herewith, and havingthe same assignee.

Having thus described certain preferred embodiments of my invention Idesire it to be understood that I am not to be limited thereby except asclaimed in view of ,prior art.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:--

1. A motor control circuit comprising in combination, a motor having afield winding andan armature winding, a source of direct-current forenergizing the field winding, a source of alternating-current, thearmature winding connected in the alternating-current circuit, twoelectronic discharge devices in the armature circuit, each device havingan anode, a cathode and a control grid, such valves oppositely connectedin parallel with each other and in series with the armature, the devicesnormally efiective to pass full-wave alternating-current to the armaturefor opposing equal torques whereby the armature is not urged torotation, means for selectively making ineffective either of saiddevices to effect a rotation of the armature in a desired direction, andmeans for causing a shifting of phase relation between the grid voltageand the plate voltage of the effective device after 'one of the deviceshas been made ineffective to vary the speed of rotation of the arma- 20ture.

2. A motor control circuit comprising in combination, a motor having afield winding and an armature winding, a source of direct-current forenergizing the field winding, a source of al- 5 ternating-current, thearmature winding connected in the alternating-current circuit, twoelectronic discharge devices in the armature circuit, each device havingan anode, a cathode and a control grid, such devices oppositely con- 3nected in parallel with each other and in series with the armature, thedevices normally eflective to pass full-wave alternating-current to thearmature for opposing equal torques whereby the armature is not urged torotation, means for selectively making ineffective either of saiddevices to effect a rotation of the armature in a grid, such devicesoppositely connected in parallel with each other and in series with thearmature, the devices normally efiective to pass fullwavealternating-current to the armature ior opposing equal torques wherebythe armature is not urged to rotation, means tor selectively makingineirective either of said devices to eiiect a rotation of the armaturein a desired direction, and means for varying the resistance in thecircuit of the eflective device after one of the devices has been made'inefi'ective to vary the speed oi rotation of the armature.

4. A motor control circuit comprising in combination, a motor having afield winding and an armature winding, a sourceoi direct-current iorenergizing the field winding, a source 01 alterhating-current. thearmature winding connected in the alternating-current circuit, twoelectronic discharge devices in the armature circuit, each device havingan anode, a cathode and a control grid, such devices oppositelyconnected in parallel with each other and in series with the armature,the devices when conducting being eflective "to pass full-wavealternating-current to the armature i'or opposing equal torques wherebythe armature is not urged to rotation, means for se' lectively allowingone of said devices to conduct current to eilect a rotation 01' thearmature in a desired direction, and means for causing a shitting ofphase relation between the grid voltage and the plate voltage oi! theconducting device after one of the devices has been made ineffective tovary the speed of rotation of the armature.

5. A motor control circuit comprising in comblnation, a motor having afield winding and an armature winding, a source of direct-current forenergizing the field winding, a source of alternating-current, thearmature winding conected in the alternating-current circuit, twoelectronic discharge devices in the armature circuit, each device havingan anode, a cathode and a control grid, such devices oppositelyconnected in parallel with each other and in series with the armature,the devices when conducting being effective to pass full-wavealternating-current to the armature for opposing equal torques wherebythe armature is not urged to rotation, means for selectively allowingone or said devices to conduct a current to eil'ect a rotation of thearmature in a desired direction, and movable means ior causing ashifting of phase relation between the grid voltage and the platevoltage of the conducting device after one of the devices has been madeineffective to vary the speed of rotation of the armature, said movablemeans shaped to give desirable relation between speed of armaturerotation and movement of the of, the movable means.

8. A motor control circuit comprising in combination, a motor having afield winding and an armature winding, a source or direct-current i'orenergizing the field winding, a source of alternating-current, thearmature winding connected in the alternating current circuit, twoelectronic discharge'devices in the armature circuit, each device havingan anode, a cathode and a control grid, such devices oppositelyconnected in parallel with each other and in series with the armature,the devices when conducting being efiective to pass full-wavealternating-current to the armature for opposing equal torques wherebythe motor is not urged to rotation,

means for selectively allowing one oi. said devices to conduct currentto eflect a rotation of the armature in a desired direction, and movablemeans for varying the inductance in the circuit or the conducting deviceafter one 0! the devices has been made effective to vary the speed ofrotation cf the armature, said movable means bination, a motor having afield winding and an armature winding, a source of direct-current forenergizing the field winding, 9. source of alternating-current, thearmature winding connected in the alternating-current circuit, twoelectronic discharge devices in the armature circuit, each device havingan anode, a cathode and a control grid, such devices oppositelyconnected in parallel with each other and in series with the armature,the devices when conducting being eiiective to pass full-wavealternatingcurrent to the armature for opposing equal torques wherebythe armature is not urged to rotation, means for selectively allowingone of said devices to conduct current to eiiect s. rotation of thearmature in a desired direction, and movable means for varying theresistance in the circuit 01' the conducting device after one 01' thedevices has been made inefi'ective to vary the speed of rotation of thearmature, said movable means comprising the movable member of anadjustable resistance, such resistance shaped to give desirable relationbetween speed 01' armature rotation and movement of said movable member.

8. A control circuit comprising in combination, a motor having a fieldwinding and an armature winding, a source of direct-current forenergizing the field winding, a source or alternating-current, thearmature winding connected in the alternating-current circuit, twoelectronic dischage devices in the armature circuit, such devicesoppositely connected in parallel with each other and in series with thear- .mature, a reactor in series with the armature and the paralleleddevices, one device effective to pass half of the alternating-currentwave to the armature, the other device normally effective to pass theopposite halt of the alternatingcurrent wave to the armature, the twohall'- waves impressed upon the armature providing opposing equaltorques-whereby the armature is not urged to rotation, means for makingineffestive one of said devices to make ineflective the torque in onedirection whereby the motor rotates in the opposite direction, and meansfor controlling the current output of the elective device after one ofthe devices has been made ineflective for varying the speed of thearmature rotatiom 9. A control circuit for a motor having a fieldwinding and an armature winding, a source of direct-current for thefield ding, a source of alternating-current and a so cc ofdirect-current for the armature, means responsive to the relationbetween the value of a variz-lble to be controlled and a predeterminedval i'or selectively impressing upon the armature windingalternating-current or direct-current, from said sources, and means forvarying the value 01' the direct-current so impressed responsive to themomentary value of the variable to be controlled.

10. A control circuit for a motor having a field winding and an armaturewinding, a source of direct-current for the field winding, analternating-current circuit, the armature winding 01' direct-current forthe field winding, an al--"- ternating-current circuit, the armaturewinding in said alternating-current circuit, a plurality 0! electronicdischarge devices in the alternating-current circuit, means forselectively making ineffective either of said devices whereby thearmature rotates in desired direction. and means for varying theinductance in the circuit 0! the effective device after one of thedevices has been made ineffective for varying ,the speed of the armaturerotation.

1 JOHN D. RYDER.

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